1. Field of the Invention
The present invention generally relates to optoelectronic integrated circuit devices, and, more particularly, to an optoelectronic integrated circuit device which performs light signal transmission between integrated circuit devices.
2. Description of the Related Art
In recent years, smaller and higher-performance electronic apparatuses of various types have been produced with the use of highly integrated, high-speed, large-scale integrated circuits (LSI). In a large-scale electric circuit such as computer, LSIs are generally mounted on a multi chip module (MCM) substrate, as shown in FIGS. 1A and 1B.
FIG. 1A is a plan view of MCM substrates 120 mounted onto a system board 110, and FIG. 1B is a side view of the MCM substrates 120.
A plurality of integrated circuit chips 130 are mounted on each of the MCM substrates 120, which electrically connect the integrated circuit chips 130. The MCM substrates 120 are mounted onto the system board 110 by inserting I/O (Input/Output) pins 160 into MCM sockets 150. The MCM substrates 120 are provided with heat radiation fins 140, if necessary. The system board 110 electrically connects the MCM substrates 120 with lead wires. Accordingly, the MCM substrates 120 and the integrated circuit chips 130 are electrically connected to one another, so that the system board 110 can have various functions.
Japanese Laid-Open Patent Application No. 5-67769 discloses such an optoelectronic integrated circuit which performs signal transmission between the integrated circuit chips 130. This optoelectronic integrated circuit is characterized by three-dimensionally arranged substrates to achieve high-speed performance and high density. In this arrangement, the substrates are perpendicular to one anther. The substrates are made of a material through which light signals can pass, so that light signal transmission can be carried out through the substrates.
Even higher speed performance is expected in an electronic apparatus provided with the MCM substrates 120 and the integrated circuit chips 130. However, the connection between the MCM substrates and the integrated circuit chips 130 are electric connection by means of lead wires patterned from a metallic material. Because of this, the signal transmission speed is limited.
As the integrated circuit chips 130 perform at higher speed, proportionally longer transmission delay time is caused in signal transmission between the MCM substrates 120 and the integrated circuit chips 130. As a result, synchronized signal transmission becomes difficult. For instance, in electric signal transmission, a transmission delay time of 70 ps/cm is caused. In FIG. 1B, a signal transmission path 170 between integrated circuit chips 130-1 and 130-2 and a signal transmission path 180 between integrated circuit chips 130-1 and 130-6 have different transmission delay times. Between the signal transmission paths 170 and 180, the difference in transmission delay time becomes too large to ignore in an operation with an operation clock speed of 5 GHz, for instance.
Also, signal damping and transmission loss are caused by the stray capacity and impedance due to the lead wires patterned from a metallic material between the MCM substrates 120 and the integrated circuit chips 130. As a result, signal transmission becomes difficult.
Meanwhile, in an optoelectronic integrated circuit for light signal transmission, light loss cannot be avoided when a light signal passes through substrates, even if the substrates are made of a material that is supposed to cause little light loss. The result is transmission loss. Such transmission loss leads to transmission errors, thereby reducing reliability in the signal transmission.
A general object of the present invention is to provide optoelectronic integrated circuit devices, in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an optoelectronic integrated circuit device which has less signal damping and transmission loss.
Another specific object of the present invention is to provide an optoelectronic integrated circuit device in which signal transmission delay time is shorter than in the prior art.
The above objects of the present invention are achieved by an optoelectronic integrated circuit device comprising a first optoelectronic integrated circuit and a second optoelectronic integrated circuit each of which includes an electric circuit unit, an optical output terminal unit having a plurality of light emitting elements connected to the electric circuit unit, and an optical input terminal unit having a plurality of light receiving elements connected to the electric circuit unit. In this optoelectronic integrated circuit device, the first optoelectronic integrated circuit and the second optoelectronic integrated circuit are arranged in such a manner that each optical output terminal unit faces each corresponding optical input terminal unit. In this arrangement, light signal transmission can be carried out between each optical output terminal unit and each corresponding optical input terminal unit of the first optoelectronic integrated circuit and the second optoelectronic integrated circuit.
Accordingly, light signal transmission can be carried out between the first optoelectronic integrated circuit and the second optoelectronic integrated circuit. Also, since each optical output terminal unit faces each corresponding optical input terminal unit, light signal transmission can be carried out without wrong transmission between substrates. Thus, signal damping and transmission loss can be reduced.
The above objects of the present invention are also achieved by a stacked optoelectronic integrated circuit device which comprises a plurality of optoelectronic integrated circuit devices each having the above structure. The plurality of optoelectronic integrated circuit devices are stacked up and bonded to each other via electrode pads.
In the stacked optoelectronic integrated circuit device having this structure, signal transmission can be carried out between the optoelectronic integrated circuit devices via the electrode pads.
The above objects of the present invention are also achieved by a multiple stacked optoelectronic integrated circuit device which comprises a plurality of stacked optoelectronic integrated circuit devices each having the above structure. The plurality of stacked optoelectronic integrated circuit devices are optically connected.
With the multiple stacked optoelectronic integrated circuit device, signal transmission delay time can be shortened, and signal damping and transmission loss can be reduced.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.